Single-walled Carbon Nanotubes Research Articles

Mechanically neutral and facile monitoring of thermoset matrices with ultrathin and highly porous carbon nanotube films

We examine how the physical features of single-walled carbon nanotube (SWCNT) thin films can affect monitoring thermoset polymers during their manufacturing and application. Film thickness (23, 37 and 53 nm), electrode materials and configuration, and embedding within or surface application on a polymer were all investigated. During manufacturing monitoring, thicker films provided higher sensitivity than thinner ones (ΔR/R0 = 111% (53 nm) vs. 74% (23 nm)). Electrode material and configuration showed that sputtered gold contacts allow higher sensitivity and reliability compared with conductive silver adhesive, and that parallel electrode placement provides more distinct and discreet stage measurements compared to diagonal one. The opposite trend was noted for mechanical loading, where thinner films provide a higher piezoresistive response and embedded films outperform surface applied sensors (gauge factors between 23-86 and 4-10, respectively). All thin films accurately measured curing stages as well as mechanical changes and are shown to be self-adjusting when the force increases during mechanical loading. We show that manufacturing monitoring should rely on uniformly deposited electrodes and thicker films for identification of polymerization stages, whereas embedding thinner films in the matrix is recommended for highly sensitive deformation monitoring. This work outlines how simple, overlooked parameters can easily be varied to optimize the dual-stage monitoring performance of CNT-based sensors and helps to identify what parameters should be chosen for specific applications.

Characterization of thin-walled self-healing microcapsules reinforced with multi-walled carbon nanotubes

This study presents a novel approach to fabricating thinner shells and significantly enhancing the fracture strength of melamine-urea-formaldehyde (M-U-F) microcapsules reinforced with multi-walled carbon nanotubes (MWCNTs). Unlike previous studies that primarily focused on single-walled carbon nanotubes (SWCNTs) or MWCNTs in polyurea-formaldehyde (PUF) shells, this research advances microcapsule technology by exploring MWCNT reinforcement in M-U-F shells. We employed a dual experimental-numerical approach, combining the precision of micro-compression tests with the predictive capabilities of finite element analysis (FEA) to determine the elastic modulus of MWCNT-reinforced M-U-F microcapsules. This method offers new insights into the mechanical behavior of these microcapsules. Our findings indicate an 8.8% increase in fracture load and a 14.6% reduction in fracture displacement for MWCNT-reinforced microcapsules compared to conventional M-U-F microcapsules. Additionally, FEA confirmed the results of the micro-compression tests, showing that MWCNT-reinforced microcapsules had the best correlation with an elastic modulus of 4.00 GPa. Conventional M-U-F microcapsules corresponded to an elastic modulus of 2.25 GPa. These results provide a comprehensive understanding of how nano-reinforcement influences the structural properties of thin-walled microcapsules, with potential applications in composite damage repair and beyond.

Diffraction features of single-walled carbon nanotubes

Diffraction features of single-walled carbon nanotubes

Nanocarbon and medicine: polymer/carbon nanotube composites for medical devices

AbstractIn view of wide-ranging application to the biomedical field, this work investigates the mechanical and electrical properties of a composite made of Single Wall Carbon Nanotubes (SWCNT) bundles self-grafted onto a poly-dimethyl-siloxane (PDMS) elastomer, particularly Sylgard 184, that has well assessed biocompatible properties and is commonly used in prosthetics. Due to the potential risks associated with the use of carbon nanostructures in implanted devices, we also assess the viability of cells directly grown on such composite substrates. Furthermore, as the stability of conductive, stretchable devices made of such composite is also crucial to their use in the medical field, we investigate, by different experimental techniques, the grafting of SWCNT bundles deep into PDMS films. Our findings prove that penetration of SWCNT bundles into the polymer bulk depends on heating time and carbon nanotubes can be seen beyond 150 μm from the surface. This is confirmed by direct electron microscopy observation of large bundles as deep as about 20 μm. The composites exhibit reliable mechanical and electrical responses that are more suitable to large and repeated deformation of the polymer with respect to thermoplastic based composites, suggesting a wide potential for their application to stretchable biomedical devices. Aiming at the proposed application of artificial bladders, a bladder prototype made of poly-dimethyl siloxane endowed with a printed SWCNT-based strain sensor was developed.

Microstructured Self-Healing Flexible Tactile Sensors Inspired by Bamboo Leaves.

Wearable electronic devices with multifunctions such as flexible, integrated, and self-powered play a crucial role in the fields of health monitoring, motion monitoring, and human-computer interaction. However, their core basic components, flexible pressure sensors, face challenges including poor long-term stability and insufficient real-time sensing accuracy. In order to solve the challenges of long-term, stable, and accurate sensing of the sensor, this paper prepares polydimethylsiloxane (SHPDMS) with intrinsic self-healing property and designs a high-sensitivity self-healing capacitive flexible pressure sensor with dual microstructures (grating microstructured electrodes and microporous dielectric layer) as the substrate based on SHPDMS. Specifically speaking, the self-healing of the sensor under mild conditions was realized by introducing reversible imine bonds with low bonding energy into the polydimethylsiloxane (PDMS) flexible substrate, which solved the problem of the material's long-term service durability. A grating-like microstructure was introduced into the flexible electrode by using a spotted bamboo taro leaf as a template, and a dual microstructure sensor was constructed by combining it with a microporous dielectric layer doped with single-walled carbon nanotubes. This way reduces the elastic modulus of the dielectric layer, improves the dielectric constant of the sensor under loading, and thus significantly improves the sensor's sensitivity and extends the measurement accuracy in a low-stress range. The prepared self-healing flexible sensor achieves a sensitivity of 3.6 kPa-1, a minimum detection limit of 5 Pa, a response recovery time of less than 80 ms, and stability over 5000 cycles, which exceeds most previously reported silicone rubber-based capacitive flexible sensors.

Single-walled carbon nanotubes hybrid carbon materials sensor for simultaneous detection of chloramphenicol and furazolidone in food samples

Single-walled carbon nanotubes hybrid carbon materials sensor for simultaneous detection of chloramphenicol and furazolidone in food samples

Near-Infrared Photoluminescence Responses of Single-Walled Carbon Nanotubes Induced by Biomolecules Detected on a Microbead Surface

Near-Infrared Photoluminescence Responses of Single-Walled Carbon Nanotubes Induced by Biomolecules Detected on a Microbead Surface

Morphology Determination of Luminescent Carbon Nanotubes by Analytical Super-Resolution Microscopy Approaches.

The ability to determine the precise structure of nano-objects is essential for a multitude of applications. This is particularly true of single-walled carbon nanotubes (SWCNTs), which are produced as heterogeneous samples. Current techniques used for their characterization require sophisticated instrumentation, such as atomic force microscopy (AFM), or compromise on accuracy. In this paper, we propose to use super-resolution microscopy (SRM) to accurately determine the morphology (orientation, length, and shape) of individual luminescent SWCNTs. We generate super-resolved images using three recently published SRM analytical software packages (DPR, eSRRF, and MSSR) and metrologically compare their performances to determine the morphological properties of SWCNTs. For this, ground-truth information on nanotube morphologies was obtained using polarization measurements and AFM to directly correlate the results from SRM at the single particle level. We show a more than 4-fold improvement in resolution over standard photoluminescence imaging, revealing hidden morphologies as efficiently as AFM. We finally demonstrate that DPR, and eventually eSRRF, can effectively assess SWCNT length distribution in a much faster and more accessible way than AFM. We believe that this approach can be generalized to other types of luminescent nanostructures and thus become a standard for rapid and accurate characterization of samples.

Boosting performance of heat-source free water-floating thermoelectric generators by controlling wettability by mixing single-walled carbon nanotubes with α-cellulose

Thermoelectric generation (TEG) using single-walled carbon nanotubes (SWCNTs), which generate electricity simply by floating on the surface of water, is promising and has novel features that are not found in conventional TEG systems. However, water-floating SWCNT-TEGs generate only a small voltage owing to the hydrophobic nature of SWCNTs. In this study, to increase their output voltage, we added α-cellulose, which is hydrophilic in nature, to the SWCNT films for enhancing water evaporative thermal cooling, leading to an increase in the temperature gradient in the TEGs. When the TEGs were exposed to artificial sunlight, the TEG with SWCNT/α-cellulose (0.6 g) films exhibited the highest output voltage of 1.0 mV, which was more than three times higher than that exhibited for the SWCNT-TEG without α-cellulose. This phenomenon can be explained by the hydrophilic nature of the films, which increases the amount of water pumped to the film surface and enhances the evaporative cooling effect as this water evaporates, thereby creating a larger temperature difference within the TEGs. The results show their significant potential as a power source for sensors such as those monitoring water flow in water environments.

Controlled Growth of Single-Walled Carbon Nanotube Films by Iron-assisted Floating Solid Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWNT) films, with exciting electronic properties are increasingly important for next-generation technologies. Here, an Iron-assisted floating solid catalyst chemical vapor deposition (IA-FSCCVD) method is developed for the controlled growth of high-quality and high-purity SWNT films. Titanium carbide nanoparticles with a high melting point are used as the solid catalysts, which provide a stable template for SWNT growth through the perpendicular growth mode. Trace amounts of iron are introduced to increase the efficiency of SWNT growth. Gas chromatography measurements and density functional theory show that the gas-phase iron acts as a pre-cracking assistance for the carbon source, promoting the growth of SWNTs. Carbon nanotube films with a high quality (average IG/ID = 166) are successfully prepared, a small diameter deviation (mean diameter of 1.6nm), and a high content of SWNTs (97%) using the IA-FSCCVD platform. This work provides a powerful way to prepare the carbon nanotube aggregates with a controlled structure.

Numerical investigation of heat and mass transfer of SWCNT/MWCNT‐water suspension over a porous stretching sheet using Sisko fluid model

AbstractThis study presents a comprehensive numerical computation of heat‐mass transfer characteristics of single‐walled carbon nanotube (SWCNT)/multi‐walled carbon nanotube (MWCNT)‐water suspension flow over a porous stretching sheet with an inclined magnetic field. The governing equations for fluid flow characteristics are formulated using the Sisko fluid model to capture the Newtonian and non‐Newtonian behavior of the nanotube‐water mixture. The nonlinear coupled partial differential equations are converted into nonlinear dimensionless coupled ordinary differential equations using suitable similarity transformations. These equations are solved using MATLAB by implementing the four‐stage Lobatto IIIa formula. The comprehensive set of computations is performed to explore the influence of pertinent parameters, including Sisko fluid parameters, concentration of nanotubes, stretching sheet velocity, and porous medium characteristics on the flow, heat, and mass transfer profiles. From the graphs and statistical analysis, it is clear that the volume fraction of SWCNT and MWCNTs are strongly correlated. The investigation reveals that increasing the inclination angle affects the fluid velocity. The variation in all flow features is negligible for volume fractions of CNTs between 0% and 10% but a significant effect is observed only beyond 10%. Higher volume fractions of CNTs result in enhanced local heat transfer coefficient. This can be attributed due to the outstanding heat transfer capabilities of CNTs owing to their high thermal conductivity. However, Shear thickening fluids exhibit high heat transfer phenomena when compared to shear‐thinning and Newtonian fluids. This research provides valuable insights into the optimization of CNT‐based nanofluids for efficient heat and mass transfer applications in electronics cooling, heat exchangers, and solar energy systems, offering opportunities to enhance energy efficiency and device performance.

Integrating Single-Walled Carbon Nanotubes into Supramolecular Assemblies: From Basic Interactions to Emerging Applications.

Integrating single-walled carbon nanotubes (SWCNTs) into supramolecular self-assemblies harnesses the distinctive mechanical, optical, and electronic properties of the nanoparticles alongside the structural and chemical properties of the assemblies. Organic molecules capable of forming supramolecular assemblies through hydrophobic, van der Waals, and π-π interactions have been demonstrated to be particularly effective in dispersing and functionalizing SWCNTs, as these same interactions facilitate the binding to the hydrophobic graphene-like surface of the SWCNTs. This review discusses a variety of self-assembling structures that were shown to integrate SWCNTs, ranging from simple micelles and ring structures to complex DNA origami and three-dimensional hydrogels formed by low-molecular-weight gelators. We explore the integration of SWCNTs into various supramolecular assemblies and highlight emerging applications of these composite materials, such as the mechanical enforcement of self-assembling hydrogels and leveraging the near-infrared (NIR) fluorescence properties of SWCNTs for monitoring the molecular self-assembly process. Notably, the distinctive NIR fluorescence of SWCNTs, which overlaps with the biological transparency window, offers significant opportunities for noninvasive sensing applications within the supramolecular platforms. Future research into a deeper understanding of the interactions between SWCNTs and different supramolecular frameworks will expand the potential applications of SWCNT-integrated supramolecular assemblies in fields like biomedical engineering, electronic devices, and environmental sensing.

Single walled carbon nanotubes/ZnO nanowires heterostructure array for NO2 gas sensing at low ppm levels

A layer-by-layer ZnO nanowire (NW)-Single Walled Carbon Nanotube (CNT) hybrid gas sensor has been proposed for effective detection of NO2 gas under a low exposure limit of 5 ppm. The fabricated hybrid sensor displayed good sensor response (S %), good selectivity and fast response time towards the target gas. S % value of 36.4 % under 5 ppm NO2 level at 250 °C and good selectivity response towards different interfering gases like SO2, CO and H2 have been observed. Meanwhile, fast response time values of 44.08 s (response) and 62.11 s (recovery) were observed at 300 °C under 5 ppm NO2 level. The sensor baseline resistance of the hybrid heterostructure (HS) was also found to be lower when compared to that of a bare ZnO NW sensor. In addition, the presence of Single Walled CNT in the HS was also shown to reduce the operational temperature of the sensor. Temperature played a significant role by controlling the adsorption and desorption kinetics of gas molecules on the surface. Moreover, the formation of p-n interface between Single Walled CNT (p-type) and ZnO NW (n-type) might have modulated the potential charge barrier on interacting with the adsorbed gases which inturn might have impacted the response of the hybrid sensor. In addition, the large surface areas offered by both NWs and nanotubes might have improved the gas adsorption capability thereby enhancing the overall hybrid sensor’s response.

Heat Transfer in Carbon-Nanotube Dispersions: A Simulation Study of the Role of Nanotube Morphology and Connectivity

Simulation of the behavior of carbon nanotubes (CNTs) can become a very challenging task considering their complicated shape and large aspect ratio. This study aims to elucidate the role of CNT shape, length, and connectivity during heat transfer in CNT dispersions through a three-dimensional (3D) simulator. Three characteristic shapes for the CNTs are considered, namely, straight, moderately curved, and strongly curved. The results reveal that the commonly used assumption of viewing CNTs as straight cylinders leads to significant overestimation of the overall medium conductivity. The CNT length has an important effect on the nanofluid conductivity for all types of CNT shapes considered here. In addition, use of CNTs with higher conductivity than a certain value appears to have no further beneficial effect, thus relaxing the need for extremely pure or single-wall CNTs. On the contrary, the conductivity remains a strong function of the CNT concentration and may be even increased upon organization of CNTs into loose clusters. The overall approach and concept can be extended to CNT composites in a straightforward manner.

Enhanced mechanical and electrical properties of single-walled carbon nanotube fibers via electric field-assisted wet spinning

Researchers have been working on creating fibers from single-walled carbon nanotubes (SWCNTs) that have optimal properties at the molecular level. However, the prepared SWCNT fibers have showed much lower properties than the ones predicted by theory because the interactions between SWCNTs and SWCNT bundles were not strong enough due to the poor alignment of SWCNTs in the fibers. In this study we improved the mechanical and electrical properties of the SWCNT fibers by using an electric field during the wet spinning process. The electric field, which was applied to the top of the syringe plunger and the tip of the spinneret, oriented the SWCNTs in the chlorosulfonic acid dope solution in a nozzle system, and made them more compact. The SWCNT fibers produced through our process exhibited a significant improvement in their properties. Specifically, we observed a 117.5 % increase in tensile strength and a 140.5 % increase in electrical conductivity. Importantly, these enhancements were achieved without the need for any additional post-treatments. This clearly demonstrates the effectiveness of our current wet spinning method.

Data-driven prediction of higher-order structure in carbon nanotube films for high thermoelectric power factor

Abstract We optimized the higher-order structures and semiconducting purity of single-walled carbon nanotubes (SWCNTs) to enhance the thermoelectric power factor PF by combining the thermoelectric random stick network (TE-RSN) method and a genetic algorithm. The PF of the optimized films was increased approximately fivefold for initial random structures. In addition, while the random structures showed the maximum PF when the ratio of semiconducting to metallic SWCNTs Rs exceeded 0.98, the optimized structures converged to an Rs of approximately 0.9. The optimized structures exhibited an increased local density and the peak of alignment angle distribution, leading to an increase in both the electrical conductivity and the Seebeck coefficient. We interpreted the increase in the Seebeck coefficient using a serial model. The results indicated that the reduction in the number of contacts within the paths and the subsequent increase in temperature difference on semiconducting SWCNTs led to the increase in the Seebeck coefficient.

Mitoxantrone release from Fmoc-protected amino acids coated magnetic carbon nanotubes: Computational and experimental study for cancer treatment

Nanoparticles have a high potential for use as drug carrier systems in cancer treatment to reduce severe side effects, as in the treatment of many other diseases. Due to their unique properties, carbon-based nanoparticles such as carbon nanotubes (CNTs) are among the most frequently used nanoparticles in drug carrier systems. In this study, magnetic single-walled CNTs (mCNTs) were synthesized, characterized, coated and their ability to carry the anticancer drug mitoxantrone (MTO) was investigated using computational and experimental methods. First, the mCNT coating capabilities of Fmoc-protected amino acids, Fmoc-Cys(trt)-OH and Fmoc-Trp-OH were demonstrated by Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Then, full-atom molecular dynamics simulations of MTO-CNT complexes in explicit water were used to understand Fmoc-amino acid and MTO loading experiments at the molecular level. Binding free energies calculated by the Molecular Mechanics/Poisson-Boltzmann Surface Area method suggested MTO-CNT complex stability even at elevated temperatures up to 350 K that can be achieved due to external magnetic stimuli. Drug loading at pH 9 and releases at physiological (pH 7.4) and lysosomal pH (pH 5.5) were carried out for uncoated and coated mCNTs. The drug release and characterization results showed that coated mCNTs have pH-responsive drug release, enhanced dispersibility, and superparamagnetic properties so they promise to be beneficial for MTO delivery in cancer treatment. Cell viability results demonstrated that the mCNT-Fmoc-Cys samples had higher cell viability compared to the mCNT and mCNT-Fmoc-Trp groups.

High-Efficiency Enzyme Assay and Screening of Enzyme-Inhibiting Nanomaterials Using Capillary Electrophoresis with Hierarchically Porous Metal-Organic Framework-Based Immobilized Enzyme Microreactor.

Enzyme-inhibiting nanomaterials have significant potential for regulating enzyme activity. However, a universal and efficient method for systematically screening and evaluating the inhibitory effects of various nanomaterials on drug target enzymes has not been established. While the integrated technique of immobilized enzyme microreactor (IMER) with capillary electrophoresis (CE) serves as an effective tool for enzyme analysis, it still faces challenges such as low enzyme loadability, unsatisfactory stability, and limited applicability. Herein, hierarchical porous metal-organic frameworks (HP-MOFs) were explored as high-performance enzyme immobilization carriers and stationary phases to develop a novel HP-MOFs-based IMER-CE microanalysis system for efficient online enzyme assay and systematic screening of enzyme-inhibiting nanomaterials. As a proof-of-concept demonstration, the model enzyme xanthine oxidase (XOD) was immobilized on a HP-UiO-66-NH2 coated capillary, serving as an efficient and durable IMER for screening potential XOD-inhibiting nanomaterials. The hierarchically micro- and mesoporous structure and superior enzyme loadability of as-prepared HP-UiO-66-NH2-IMER was intensively characterized, followed by systematic evaluation of the separation performance of HP-UiO-66-NH2 coated column and the enzyme kinetics of the immobilized XOD. Compared to the microporous UiO-66-NH2-IMER, the HP-UiO-66-NH2-IMER-CE system showed significant improvements in enzyme loading, maximum reaction rate, repeatability, and long-term stability. Furthermore, the established method was effectively employed to screen the XOD inhibitory activity of various nanomaterials, revealing that graphene oxide, single wall carbon nanotube and three other nanomaterials exhibited inhibitory potentials. The HP-MOFs-based microanalysis system can be easily expanded by modifying the types of immobilized enzymes and holds the potential to accelerate the identification and rational design of effective enzyme-inhibiting nanomaterials.

Preparation of a V–COF@SWCNTs-COOH/SPCE supported molecularly imprinted electrochemical sensor for real-time detection of trace sulfadimidine

To overcome the limitations of insufficient sensitivity and poor specificity of portable screen-printed carbon electrode-electrochemical sensors (SPCE-EC) in practical applications, we prepared carrier composites of carboxylic single-walled carbon nanotubes vertically grafted by covalent organic frameworks (v-COF@SWCNTs-COOH) and coated with a molecularly imprinted polymer (MIP) of sulfadimidine (SM2). 55 °C hot steam elution is more eco-friendly than traditional organic solvent elution. The results showed that when the mass ratio of DBA to DBA-SWCNTs was 1:1, the v-COF@SWCNTs-COOH obtained by the two-step synthesis method could increase the electrical signal up to 2.33-fold of the bare electrode. The bifunctional monomer MIP prepared on the above structure enhanced the signal response by 2.91-fold, with a high imprint factor of 20. The assembled MIP/v-COF@SWCNTs-COOH/SPCE were analyzed by differential pulse voltammetry (DPV) with a high sensitivity of 0.21 nM for LOD and 0.70 nM for LOQ. In milk and fish samples, the recovery rate was 95.0 %–104.8 %. The validation of authentic pork samples with the statutory LC-MS/MS method showed no significant difference (P > 0.05). The sensor's performance indicators remained robust after five repeated uses. Therefore, the MIP/v-COF@SWCNTs-COOH/SPCE combines the cheapness and portability of SPCE, while the sensitivity and specificity of small molecule detection were significantly improved.

Fabrication of carbon nanotube neuromorphic thin film transistor arrays and their applications for flexible olfactory-visual multisensory synergy recognition

Abstract Artificial multisensory devices play a key role for the human-computer interaction in the field of artificial intelligence (AI). In this work, we have designed and constructed a novel olfactory-visual bimodal neuromorphic carbon nanotube thin film transistor (TFT) arrays for artificial olfactory-visual multisensory synergy recognition with the ultralow single-pulse power consumption of 25 aJ, employing semiconducting single-walled carbon nanotubes (sc-SWCNTs) as channel materials and gas sensitive materials, and poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b0]dithiophene-2,6-diyl]-2,5-thiophenediyl-[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c0]dithio-phene-1,3-diyl]] (PBDB-T) as the photosensitive material. It is noted that it is the first time to realize the simulation of olfactory and visual senses (from 280 nm to 650 nm) with the wide operating temperature range (0-150 °C) in a single SWCNT TFT device and successfully simulate the recovery of olfactory senses after COVID-19 by olfactory-visual synergy. Furthermore, our SWCNT neuromorphic TFT devices with high Ion/Ioff ratio (up to 106) at a low operating voltage (-2-0.5 V) can mimic not only the basic biological synaptic functions of olfaction and vision (such as paired-pulse facilitation, short-term plasticity, and long-term plasticity), but also optical wireless communication by Morse code. The proposed multisensory, broadband light-responsive, low-power synaptic devices provide great potential for developing AI robots to face complex external environments.